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Example Low Power Use Cases
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SPRAC74A–February 2017–Revised March 2017
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Copyright © 2017, Texas Instruments Incorporated
AM335x Low Power Design Guide
OPP Summary
The AM335x has several pre-defined Operating Performance Points (OPPs). Each OPP specifies a
frequency and voltage pairing for the MPU and core power domains. Table 3 summarizes the OPPs used
in this document and the voltage and frequency specifications of each.
Table 3. AM335x MPU Supported Operating Performance Points
OPP
Frequency (MHz) Voltage (V)
MPU MPU
OPP50 300 0.95
OPP100 600 1.1
OPP120 720 1.2
Turbo 800 1.26
Nitro 1000 1.325
Table 4. AM335x Core Supported Operating Performance Points
VDD_CORE
OPP VDD_CORE (V)
Frequency (MHz)
mDDR DDR2 DDR3/ DDR3L L3 L4
OPP50 0.95 90 125 - 100 50
OPP100 1.10 200 266 400 200 100
This OPP data is provided as a reference only for Silicon Revision "A" or higher. For full details on
recommended OPPs and limitations, see Section 5.4 in the AM335x Sitara™ Processors Data Manual.
Due to errata Advisory 1.0.24 - Boot: System Boot is Not reliable if Reset is Asserted While Operating in
OPP50, supporting Core OPP50 requires that the voltages remain at OPP100 levels during system reset.
In addition, according to errata Advisory 1.0.15 - ARM Cortex-A8: OPP50 on MPU Domain Not Supported
running Core OPP50, running Core OPP50 requires OPP100 voltage levels to ensure stability, this applies
to the Sillicon revision 1.0 hardware only. More information about these errata can be found in the
AM335x Sitara™ Processors Silicon Revisions 2.1, 2.0, 1.0 Silicon Errata.
All test cases are run at Core OPP100.
To specify the MPU OPP, control over the CPU frequency must be given to userspace, and then the
desired frequency can be selected:
Userspace MPU Frequency Selection
$ echo userspace > /sys/device/system/cpu/cpu0/cpufreq/scaling_governor
$ echo $FREQ_IN_KHZ > /sys/device/system/cpu/cpu0/cpufreq/scaling_setspeed
To view available frequencies:
Show Available MPU Frequencies
$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
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